Update Duo Chat how-to documentation

What does this merge request do and why?

• Move "Evaluation datasets" into the "Type of evaluations" AND add the dataset mapping to the input adapter.
• Move "Metrics" together with "Type of evaluations" to the top
• Merge "Configuration file" with "Configuration options"
• Update the GCP authentication to use a personal GCP account with gcloud auth command instead of a shared service account. Highlight that this is required to write/read to BigQuery and call Vertex AI models.
• Remove the Docker setup. Promote running it locally.
• Expand the inspecting result section to guide users on what to compare given the metrics selected in the evaluation. For example, if the similarity score is selected, please compare with the similarity score column in the control table.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• I've ran the affected pipeline(s) to validate that nothing is broken.
• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.

Relates to #222